This invention applies to vehicle suspensions for free rolling axles (non-driving axles). More specifically this suspension may be preferably used with axles that are arranged in multiple axle clusters. These clusters can have two axle assemblies mounted laterally displaced from each other across the width of the vehicle, and one or more (typically 2, 3, or 4) lines of such axles mounted along the length of the vehicle. In most cases the vehicle is a trailer, but may also be a powered vehicle with auxiliary free rolling axles.
Similar art in the field is listed as follows.
References U.S. Patents
    U.S. Pat. No. 4,166,640—Van Denberg—Turner suspension with “Tri-Functional” pivot bushing.    U.S. Pat. No. 4,732,407—Oyama—Fuji use of variable rate bushing.    U.S. Pat. No. 5,037,126—Gottschalk—Boler (Hendrickson) trailing arm construction.    U.S. Pat. No. 5,996,981—Dilling—Boler (Hendrickson) narrow bushing.    U.S. Pat. No. 7,108,270—Smith—Cantilever axle suspension, non roll linked.    U.S. Pat. No. 6,142,496—Bartel—Cantilever axle suspension, roll linked.    U.S. Pat. No. 6,286,857—Reese, et al—Trunnion axle suspension.    U.S. Pat. No. 7,077,410—Gregg, et al—Trunnion axle suspension
In preferred applications, this type of suspension utilizes “air springs” to support the load carried by the trailer chassis frame with pneumatic pressure. The air springs also deflect to absorb bumps and uneven road surfaces. Air springs bring the advantage that their spring schedule may be adjusted, allowing for customization of clearance and reaction characteristics. Interconnecting the air springs for groups of axles with pneumatic hose or pipe allows equal pressure to be applied to groups of axles, permitting the load on each axle within the connected group to carry a relatively equal portion of the total load (axle equalization). Alternative types of resilient cushioning members may be used in place of the air springs. These could include, but are not limited to, hydraulic cylinders, hydraulic cylinders with gas charged accumulators, elastomeric cushions, steel springs, or combinations of spring types.
This invention particularly and preferably relates to multiwheel axles carried by a trailing arm suspension that permits an axle to rotate to a limited degree about the longitudinal axis of the trailing arm. This is desirable in order to maintain ground contact and equal wheel loading for the wheels on both ends of the individual axle. A trailing arm of such a suspension is also pivotally attached to the vehicle chassis frame such that the pivot joint allows the trailing arm to rotate in a vertical plane, thus allowing the wheel axle to rise and fall according to irregularities in the road surface. The springs positioned between the trailing arm and the chassis frame remote from the trailing arm pivot joint limit the degree of trailing arm rotation in the vertical plane as well as providing support to the chassis frame.
While the ability of the trailing arm to swing in a vertical plane allows the wheel axle to move upward and downward with respect to the vehicle frame, there is a need in such vehicle suspensions to provide resistance to lateral deflections of the trailing arm. Prior art suspensions have used either a heavy duty resilient compound trunnion pivot (Gregg, et al—U.S. Pat. No. 7,077,410), or a sliding guide at the rear end of the trailing arm (Reese, et al—U.S. Pat. No. 6,286,857), or a Panhard Rod to resist lateral deflection. These lateral forces may be significant as they are caused by centrifugal turning forces, the lateral component of gravitational forces when the vehicle is on banked surfaces and, most significantly, the lateral wheel skid force created when a cluster of axles distributed along the length of the vehicle frame is exposed to turning forces. During turning the forward axles in the cluster must skid toward the inside of the turn, while the rear axles skid toward the outside of the turn. These “skid steer” forces are relatively high due to the coefficient of friction of the tires (grip) and irregularities (ruts) in the road surface. Accordingly, there is a need for a trailing arm to resist excessive lateral deflections of such arm, out of alignment with the vehicle longitudinal axis, without necessarily incurring the relative complexity of a resilient trunnion pivot or the increased suspension construction and maintenance costs usually associated with sliding guide and Panhard Rod based designs.
There is also a need for a suspension to resist lateral roll or sway of the vehicle frame or chassis to which it is mounted. To resist such lateral roll or sway of the chassis, a relatively parallel alignment of the right and left side trailing arms should be maintained. This is the function of a typical anti-sway bar, when employed. However, in many prior art suspensions systems such supplementary anti-roll features are not provided. As a result roll stability is primarily the function of the suspension spring rate (spring stiffness) and lateral trailing arm spacing (stance), thus these suspensions tend to have low roll stability.
In this context, there is a need for an improved arrangement for limiting undesired deflections in a trailing arm, while permitting the desired degree of flexibility. This invention addresses that objective.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.